The following abbreviations and terms are herewith defined, at least some of which are referred to within the following description of the present disclosure.
3GPP 3rd-Generation Partnership Project
ACK Acknowledge
AGCH Access Grant Channel
ARQ Automatic Repeat Request
ASIC Application Specific Integrated Circuit
BLER Block Error Rate
BLKS Blocks
BSC Base Station Controller
BSS Base Station Subsystem
BSSGP Base Station Subsystem GPRS Protocol
BTS Base Transceiver Station
CC Coverage Class
CN Core Network
DL Downlink
DSP Digital Signal Processor
DRX Discontinuous Receive
eDRX Extended Discontinuous Receive
EC-GSM Extended Coverage-Global System for Mobile Communications
EC-PCH Extended Coverage Paging Channel
EC-SCH Extended Coverage Synchronization Channel
EDGE Enhanced Data rates for GSM Evolution
EGPRS Enhanced General Packet Radio Service
E-UTRA Evolved Universal Terrestrial Radio Access
FCCH Frequency Correction Channel
GSM Global System for Mobile Communications
GERAN GSM/EDGE Radio Access Network
GPRS General Packet Radio Service
HARQ Hybrid ARQ
IE Information Element
IMSI International Mobile Subscriber Identity
IoT Internet of Things
IP Internet Protocol
LAN Local Area Network
LL Logical Link
LLGMM Logical Link GPRS Mobility Management
LLC Logical Link Control
LLSMS Logical Link Short Message Service
LTE Long-Term Evolution
MAC Media Access Control
MCS Modulation and Coding Scheme
MFRM Multiframe
MTC Machine Type Communications
NAS Non-Access Stratum
PCH Paging Channel
PDA Personal Digital Assistant
PDTCH Packet Data Traffic Channel
PDU Protocol Data Unit
PLMN Public Land Mobile Network
PSTN Public Switched Telephone Network
RACH Random Access Channel
RAM Random Access Memory
RAN Radio Access Network
RAT Radio Access Technology
RAU Routing Area Update
RBS Radio Base Station
RCC Radio Coverage Category
RLC Radio Link Control
RNC Radio Network Controller
ROM Read-Only Memory
RRC Radio Resource Control
SAPI Service Access Point Identifier
SCH Synchronization Channel
SGSN Serving GPRS Support Node
SMS Short Message Service
TBF Transport Block Format
TDMA Time Division Multiple Access
TLLI Temporary Logical Link Identifier
TOM Tunneling of Messages
TR Technical Report
TS Technical Specification
UE User Equipment
UL Uplink
VoIP Voice over Internet Protocol
WAN Wide Area Network
WCDMA Wideband Code Division Multiple Access
WiMAX Worldwide Interoperability for Microwave Access
WLAN Wireless Local Area Network
Coverage Class: At any point in time a device belongs to a specific uplink/downlink coverage class that corresponds to either the legacy radio interface performance attributes that serve as the reference coverage for legacy cell planning (e.g., a Block Error Rate of 10% after a single radio block transmission on the PDTCH) or a range of degraded radio interface performance attributes compared to the reference coverage (e.g., up to 4 dB lower performance than that of the reference coverage). Coverage class determines the total number of blind repetitions to be used when transmitting/receiving radio blocks. An uplink/downlink coverage class applicable at any point in time can differ between different logical channels. Upon initiating a system access a device determines the uplink/downlink coverage class applicable to the RACH/AGCH based on estimating the number of blind repetitions of a radio block needed by the BSS receiver/device receiver to experience a BLER (block error rate) of approximately 10%. The BSS determines the uplink/downlink coverage class to be used by a device on the device's assigned packet channel resources based on estimating the number of blind repetitions of a radio block needed to satisfy a target BLER and considering the number of HARQ retransmissions (of a radio block) that will, on average, result from using that target BLER.Note: a device operating with radio interface performance attributes corresponding to the reference coverage is considered to be in the best coverage class (i.e., coverage class 1) and therefore does not make blind repetitions.eDRX cycle: eDiscontinuous reception (eDRX) is a process of a wireless device disabling its ability to receive when it does not expect to receive incoming messages and enabling its ability to receive during a period of reachability when it anticipates the possibility of message reception. For eDRX to operate, the network coordinates with the wireless device regarding when instances of reachability are to occur. The wireless device will therefore wake-up and enable message reception only during pre-scheduled periods of reachability. This process reduces the power consumption which extends the battery life of the wireless device and is sometimes called sleep mode.Extended Coverage: The general principle of extended coverage is that of using blind repetitions for the control channels and for the data channels. In addition, for the data channels the use of blind repetitions assuming MCS-1 (i.e., the lowest MCS supported in EGPRS today) is combined with HARQ retransmissions to realize the needed level of data transmission performance. Support for extended coverage is realized by defining different coverage classes. A different number of blind repetitions are associated with each of the coverage classes wherein extended coverage is associated with coverage classes for which one or more blind repetitions are needed (i.e., an initial transmission without any subsequent blind repetitions is considered as the reference coverage). The number of total blind repetitions for a given coverage class (except coverage class 1) can differ between different logical channels. Note: a wireless device using coverage class 1 on the uplink only transmits a single instance of a radio block it sends on any given logical channel (i.e., no blind repetitions are needed). Similarly, a wireless device using coverage class 1 on the downlink is only sent a single instance of a radio block on any given logical channel (i.e., no blind repetitions are needed).Nominal Paging Group: The specific set of EC-PCH blocks a device monitors once per eDRX cycle. The device determines this specific set of EC-PCH blocks using an algorithm that takes into account its IMSI, its eDRX cycle length and its downlink coverage class.
The anticipated ubiquitous deployment of wireless devices used for what is known as Machine-Type-Communication (MTC) will result in wireless devices being placed outside the typical radio coverage of the existing radio networks, e.g., in basements and similar locations. One way to improve the radio coverage is by expanding the radio access network infrastructure, such as by adding additional Radio Base Station (RBS) equipment. This, however, may very quickly result in an unreasonable investment effort and may not be acceptable to operators.
An alternative approach to adding additional equipment is to keep the existing radio access network infrastructure unchanged but instead improve the radio coverage through novel radio transmission and reception techniques as well as new Radio Resource Management algorithms. The alternative approach is currently being discussed in the wireless industry and is a subject for a standardization effort, for example, in the 3rd-Generation Partnership Project (3GPP) as described in the 3GPP TR 36.824 V11.0.0 Technical Report, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); LTE coverage enhancements” and the 3GPP TSG-GERAN Meeting #62 Work Item Description GP-140421, entitled “New Study Item on Cellular System Support for Ultra Low Complexity and Low Throughput Internet of Things.” The contents of these two documents are hereby incorporated herein by reference for all purposes.
While there are many techniques that can be used to enhance the radio coverage as discussed above, one technique that is of particular interest in the present disclosure is to enhance the radio coverage through the use of repeated transmissions (blind repetitions) based on coverage classes (CCs). The repeated transmissions technique is currently being considered in the context of the standardization work in 3GPP TSG RAN, as described in the above-referenced 3GPP TR 36.824 V11.0.0 Technical Report, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); LTE coverage enhancements” as well as in 3GPP TR 45.820 V1.3.0 Technical Report, entitled “Cellular System Support for Ultra Low Complexity and Low Throughput Internet of Things”. The contents of these two documents are hereby incorporated herein by reference for all purposes.
As also described in 3GPP TSG-GERAN Meeting #63 Tdoc GP-140605, entitled “GSM Evolution for cellular IoT—PCH Overview” (the contents of which are incorporated herein by reference), wireless devices (e.g., those used for machine type communications (MTC)) can operate using different coverage classes and can be expected to make use of different extended discontinuous receive (eDRX) cycles ranging from minutes to hours or even days depending on the frequency of reachability desired for such wireless devices. As such, these wireless devices can transmit information to the radio access network (RAN) regarding their current (i.e., currently estimated) coverage class and eDRX cycle length within Radio Resources Control (RRC) or Non-Access Stratum (NAS) messages (e.g., GPRS Attach or Routing Area Update messages), thereby allowing the RAN node (e.g., BSS) or the Core Network node (e.g., SGSN) to determine the current coverage class and the periodicity with which the wireless devices will wake-up to look for a page according to their nominal paging group associated within their current coverage class and eDRX cycle. The total number of paging resources (paging blocks) per desired eDRX cycle can be determined based on coverage class, since each coverage class will need a different number of Paging Channel (PCH) block repetitions within the context of a single paging group. For example, considering a wireless communication network wherein a single 51-multiframe supports 8 PCH blocks, it can be the case where the desired eDRX cycle Y=256 51-multiframes ≈60 seconds (e.g., exactly 208 of these DRX cycles will occur within the overall TDMA Frame Number (FN) space of 2715648 TDMA frames). Accordingly, the number of paging groups supported within eDRX cycle Y can be determined by the coverage class of a wireless device that operates using that eDRX cycle as follows:                PCH blocks per eDRX cycle =PB_DRX_CYCLE=256×8=2048.        Coverage Class 1: Paging groups per eDRX cycle Y=PB_DRX_CYCLE=2048        Coverage Class 2: Paging groups per eDRX cycle Y=PB_DRX_CYCLE div 2=1024        Coverage Class 3: Paging groups per eDRX cycle Y=PB_DRX_CYCLE div 4=512        Coverage Class 4: Paging groups per eDRX cycle Y=PB_DRX_CYCLE div 8=256        Coverage Class 5: Paging groups per eDRX cycle Y=PB_DRX_CYCLE div 16=128        
In view of the existing solutions, there are still problems associated with the repeated transmissions technique based on coverage classes. First of all, there is in principal no procedure available for a wireless device (e.g., EC-GSM device) to convey a change of its coverage class to the network (e.g., SGSN) other than via a Routing Area Update Procedure, which is very signalling intensive and is as such not suitable for wireless devices targeting a 10 year battery life time. Further, since the Routing Area Update procedure is very signalling intensive it adds signalling load to both the radio network interfaces and the core network interfaces. Second, the current proposals for the network (e.g., RAN node, BSS) to manage the paging groups for wireless devices are not optimized to handle a change in the DL CC just prior to the next occurrence of the nominal paging group for a given wireless device. These problems are discussed in more detail as follows:                If the SGSN (network) is informed of the new DL CC shortly before the next occurrence of the nominal paging group based on the old DL CC and this results in a new nominal paging group that occurs well into the future compared to its old nominal paging group (e.g., 20 minutes), then this can effectively result in an excessively deferred paging opportunity.        If a wireless device determines its paging group based on the current procedure, by mod(IMSI,N), where N is the number of paging groups within the eDRX cycle and the result of the operation is the paging block(s) to be monitored by the wireless device, then the nominal paging group for a given coverage class can occur uncorrelated from the nominal paging group associated with another coverage class, within the same eDRX cycle.        In FIG. 1 (PRIOR ART) there is an illustration showing the current paging group procedure and the problem associated therewith within the context of four 51 multiframes 102a, 102b, 102c and 102d (around 1 second) where the difference between nominal paging groups (see patterned boxes) for different coverage classes namely CC1, CC2, CC3, CC4, CC5 and CC6 for the same wireless device could be as long as the full eDRX cycle (several minutes). This implies that the reachability pattern of the wireless device can be substantially impacted by changing the DL CC while maintaining the same eDRX cycle length.        
These problems and other problems associated with the state-of-the-art are addressed by the present disclosure.